317 lines
12 KiB
C++
317 lines
12 KiB
C++
// MFEM Example 6 - Parallel Version
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//
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// Compile with: make ex6p
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//
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// Sample runs: mpirun -np 4 ex6p -m ../data/square-disc.mesh -o 1
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// mpirun -np 4 ex6p -m ../data/square-disc.mesh -o 2
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// mpirun -np 4 ex6p -m ../data/square-disc-nurbs.mesh -o 2
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// mpirun -np 4 ex6p -m ../data/star.mesh -o 3
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// mpirun -np 4 ex6p -m ../data/escher.mesh -o 2
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// mpirun -np 4 ex6p -m ../data/fichera.mesh -o 2
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// mpirun -np 4 ex6p -m ../data/disc-nurbs.mesh -o 2
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// mpirun -np 4 ex6p -m ../data/ball-nurbs.mesh
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// mpirun -np 4 ex6p -m ../data/pipe-nurbs.mesh
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// mpirun -np 4 ex6p -m ../data/star-surf.mesh -o 2
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// mpirun -np 4 ex6p -m ../data/square-disc-surf.mesh -o 2
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// mpirun -np 4 ex6p -m ../data/amr-quad.mesh
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//
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// Description: This is a version of Example 1 with a simple adaptive mesh
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// refinement loop. The problem being solved is again the Laplace
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// equation -Delta u = 1 with homogeneous Dirichlet boundary
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// conditions. The problem is solved on a sequence of meshes which
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// are locally refined in a conforming (triangles, tetrahedrons)
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// or non-conforming (quadrilaterals, hexahedra) manner according
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// to a simple ZZ error estimator.
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//
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// The example demonstrates MFEM's capability to work with both
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// conforming and nonconforming refinements, in 2D and 3D, on
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// linear, curved and surface meshes. Interpolation of functions
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// from coarse to fine meshes, as well as persistent GLVis
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// visualization are also illustrated.
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//
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// We recommend viewing Example 1 before viewing this example.
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#include "mfem.hpp"
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#include <fstream>
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#include <iostream>
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using namespace std;
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using namespace mfem;
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int main(int argc, char *argv[])
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{
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// 1. Initialize MPI.
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int num_procs, myid;
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MPI_Init(&argc, &argv);
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MPI_Comm_size(MPI_COMM_WORLD, &num_procs);
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MPI_Comm_rank(MPI_COMM_WORLD, &myid);
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// 2. Parse command-line options.
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const char *mesh_file = "../data/star.mesh";
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int order = 1;
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bool pa = false;
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bool cuda = false;
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bool omp = false;
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bool raja = false;
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bool occa = false;
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bool visualization = true;
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OptionsParser args(argc, argv);
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args.AddOption(&mesh_file, "-m", "--mesh",
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"Mesh file to use.");
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args.AddOption(&order, "-o", "--order",
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"Finite element order (polynomial degree).");
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args.AddOption(&pa, "-p", "--pa", "-no-p", "--no-pa",
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"Enable Partial Assembly.");
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args.AddOption(&cuda, "-cu", "--cuda", "-no-cu", "--no-cuda", "Enable CUDA.");
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args.AddOption(&omp, "-om", "--omp", "-no-om", "--no-omp", "Enable OpenMP.");
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args.AddOption(&raja, "-ra", "--raja", "-no-ra", "--no-raja", "Enable RAJA.");
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args.AddOption(&occa, "-oc", "--occa", "-no-oc", "--no-occa", "Enable OCCA.");
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args.AddOption(&visualization, "-vis", "--visualization", "-no-vis",
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"--no-visualization",
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"Enable or disable GLVis visualization.");
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args.Parse();
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if (!args.Good())
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{
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if (myid == 0)
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{
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args.PrintUsage(cout);
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}
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MPI_Finalize();
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return 1;
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}
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if (myid == 0)
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{
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args.PrintOptions(cout);
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}
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// 3. Read the (serial) mesh from the given mesh file on all processors. We
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// can handle triangular, quadrilateral, tetrahedral, hexahedral, surface
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// and volume meshes with the same code.
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Mesh *mesh = new Mesh(mesh_file, 1, 1);
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int dim = mesh->Dimension();
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int sdim = mesh->SpaceDimension();
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if (pa) { mesh->EnsureNodes(); }
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// 4. Refine the serial mesh on all processors to increase the resolution.
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// Also project a NURBS mesh to a piecewise-quadratic curved mesh. Make
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// sure that the mesh is non-conforming.
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if (mesh->NURBSext)
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{
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mesh->UniformRefinement();
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mesh->SetCurvature(2);
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}
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mesh->EnsureNCMesh();
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// 5. Define a parallel mesh by partitioning the serial mesh.
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// Once the parallel mesh is defined, the serial mesh can be deleted.
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ParMesh pmesh(MPI_COMM_WORLD, *mesh);
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delete mesh;
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MFEM_VERIFY(pmesh.bdr_attributes.Size() > 0,
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"Boundary attributes required in the mesh.");
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Array<int> ess_bdr(pmesh.bdr_attributes.Max());
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ess_bdr = 1;
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// 6. Define a finite element space on the mesh. The polynomial order is
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// one (linear) by default, but this can be changed on the command line.
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H1_FECollection fec(order, dim);
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ParFiniteElementSpace fespace(&pmesh, &fec);
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// 7. Set MFEM config parameters from the command line options
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if (cuda) { config::UseCuda(); }
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if (omp) { config::UseOmp(); }
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if (raja) { config::UseRaja(); }
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if (occa) { config::UseOcca(); }
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config::EnableDevice();
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// 8. As in Example 1p, we set up bilinear and linear forms corresponding to
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// the Laplace problem -\Delta u = 1. We don't assemble the discrete
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// problem yet, this will be done in the main loop.
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AssemblyLevel assembly = (pa) ? AssemblyLevel::PARTIAL : AssemblyLevel::FULL;
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int elem_batch = (pa) ? pmesh.GetNE() : 1;
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ParBilinearForm a(&fespace, assembly, elem_batch);
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ParLinearForm b(&fespace);
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ConstantCoefficient one(1.0);
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BilinearFormIntegrator *integ = new DiffusionIntegrator(one);
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a.AddDomainIntegrator(integ);
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b.AddDomainIntegrator(new DomainLFIntegrator(one));
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// 9. The solution vector x and the associated finite element grid function
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// will be maintained over the AMR iterations. We initialize it to zero.
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ParGridFunction x(&fespace);
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x = 0;
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// 10. Connect to GLVis.
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char vishost[] = "localhost";
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int visport = 19916;
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socketstream sout;
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if (visualization)
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{
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sout.open(vishost, visport);
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if (!sout)
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{
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if (myid == 0)
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{
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cout << "Unable to connect to GLVis server at "
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<< vishost << ':' << visport << endl;
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cout << "GLVis visualization disabled.\n";
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}
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visualization = false;
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}
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sout.precision(8);
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}
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// 11. Set up an error estimator. Here we use the Zienkiewicz-Zhu estimator
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// with L2 projection in the smoothing step to better handle hanging
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// nodes and parallel partitioning. We need to supply a space for the
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// discontinuous flux (L2) and a space for the smoothed flux (H(div) is
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// used here).
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L2_FECollection flux_fec(order, dim);
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ParFiniteElementSpace flux_fes(&pmesh, &flux_fec, sdim);
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RT_FECollection smooth_flux_fec(order-1, dim);
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ParFiniteElementSpace smooth_flux_fes(&pmesh, &smooth_flux_fec);
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// Another possible option for the smoothed flux space:
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// H1_FECollection smooth_flux_fec(order, dim);
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// ParFiniteElementSpace smooth_flux_fes(&pmesh, &smooth_flux_fec, dim);
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L2ZienkiewiczZhuEstimator estimator(*integ, x, flux_fes, smooth_flux_fes);
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// 12. A refiner selects and refines elements based on a refinement strategy.
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// The strategy here is to refine elements with errors larger than a
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// fraction of the maximum element error. Other strategies are possible.
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// The refiner will call the given error estimator.
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ThresholdRefiner refiner(estimator);
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refiner.SetTotalErrorFraction(0.7);
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// 13. The main AMR loop. In each iteration we solve the problem on the
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// current mesh, visualize the solution, and refine the mesh.
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const int max_dofs = 100000;
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for (int it = 0; ; it++)
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{
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HYPRE_Int global_dofs = fespace.GlobalTrueVSize();
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if (myid == 0)
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{
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cout << "\nAMR iteration " << it << endl;
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cout << "Number of unknowns: " << global_dofs << endl;
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}
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// 14. Assemble the right-hand side and determine the list of true
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// (i.e. parallel conforming) essential boundary dofs.
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Array<int> ess_tdof_list;
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fespace.GetEssentialTrueDofs(ess_bdr, ess_tdof_list);
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b.Assemble();
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// 15. Switch back to the device and assemble the stiffness matrix. Note
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// that MFEM doesn't care at this point that the mesh is nonconforming
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// and parallel. The FE space is considered 'cut' along hanging
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// edges/faces, and also across processor boundaries.
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config::SwitchToDevice();
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a.Assemble();
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// 16. Create the parallel linear system: eliminate boundary conditions.
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// The system will be solved for true (unconstrained/unique) DOFs only.
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Vector B, X;
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Operator *A;
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if (!pa) { A = new HypreParMatrix(); }
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const int copy_interior = 1;
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a.FormLinearSystem(ess_tdof_list, x, b, A, X, B, copy_interior);
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// 17. Solve the linear system A X = B.
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if (!pa)
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{
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// Parallel PCG solver with the BoomerAMG preconditioner from hypre.
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HypreParMatrix &H = *static_cast<HypreParMatrix*>(A);
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HypreBoomerAMG amg;
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amg.SetPrintLevel(0);
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CGSolver pcg(H.GetComm());
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pcg.SetPreconditioner(amg);
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pcg.SetOperator(H);
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pcg.SetRelTol(1e-6);
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pcg.SetMaxIter(200);
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pcg.SetPrintLevel(3); // print the first and the last iterations only
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pcg.Mult(B, X);
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}
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else
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{
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// No preconditioning for now in partial assembly mode.
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CGSolver cg(MPI_COMM_WORLD);
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cg.SetRelTol(1e-12);
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cg.SetMaxIter(2000);
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cg.SetPrintLevel(3);
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cg.SetOperator(*A);
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cg.Mult(B, X);
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}
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// 18. Switch back to the host and extract the parallel grid function
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// corresponding to the finite element approximation X. This is the
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// local solution on each processor.
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config::SwitchToHost();
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a.RecoverFEMSolution(X, b, x);
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// 19. Send the solution by socket to a GLVis server.
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if (visualization)
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{
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sout << "parallel " << num_procs << " " << myid << "\n";
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sout << "solution\n" << pmesh << x << flush;
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}
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if (global_dofs > max_dofs)
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{
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if (myid == 0)
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{
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cout << "Reached the maximum number of dofs. Stop." << endl;
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}
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break;
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}
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// 20. Call the refiner to modify the mesh. The refiner calls the error
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// estimator to obtain element errors, then it selects elements to be
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// refined and finally it modifies the mesh. The Stop() method can be
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// used to determine if a stopping criterion was met.
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refiner.Apply(pmesh);
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if (refiner.Stop())
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{
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if (myid == 0)
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{
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cout << "Stopping criterion satisfied. Stop." << endl;
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}
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break;
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}
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// 21. Update the finite element space (recalculate the number of DOFs,
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// etc.) and create a grid function update matrix. Apply the matrix
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// to any GridFunctions over the space. In this case, the update
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// matrix is an interpolation matrix so the updated GridFunction will
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// still represent the same function as before refinement.
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fespace.Update();
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x.Update();
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// 22. Load balance the mesh, and update the space and solution. Currently
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// available only for nonconforming meshes.
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if (pmesh.Nonconforming())
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{
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pmesh.Rebalance();
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// Update the space and the GridFunction. This time the update matrix
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// redistributes the GridFunction among the processors.
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fespace.Update();
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x.Update();
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}
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// 23. Inform also the bilinear and linear forms that the space has
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// changed.
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a.Update();
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b.Update();
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delete A;
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}
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MPI_Finalize();
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return 0;
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}
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